The present invention relates to an image forming apparatus of the type using all electrophotographic procedure and, more particularly, to an image forming apparatus capable of producing a stable and clear-cut image at all times.
A prerequisite for an electrophotographic copier, facsimile machine, laser printer or similar image forming apparatus is that it produces an image with stable density and clear-cutness over a long period of time. An electrophotographic copier, for example, has a photoconductive element which is implemented by OPC or selenium-based organic semiconductor. A photoconductive element using OPC in particular has a problem that a surface potential thereof, especially in a comparatively low potential area, is susceptible to a change in surface temperature and deterioration. Hence, an electrophotographic copier with an OPC photoconductive element causes the background of a reproduction to be blurred or an image to be lost after a long time of use, even though it may be provided with an expedient for controlling toner density.